The Vidua finches, including 10 species of indigobirds and 9 long-tailed whydahs (Sorenson et al. 2004), are of particular interest to ornithologists because of their high degree of host-specificity and their relatively benign effects on hosts as compared to other parasitic birds. Most species of indigobirds parasitize a single species of firefinch in the genus Lagonosticta (Payne 1996), although recent field studies (Payne et al. 1992, 2005; Payne & Payne 1994, 1995) have shown that indigobirds parasitize four additional estrildid finch species in four different genera (Table 1). The host-specificity of indigobirds is evidenced in two remarkable ways. First, nestling indigobirds are reared along with the host’s own young and young indigobirds mimic the mouth markings and begging behavior of their respective hosts (Nicolai 1964). Young firefinches and other estrildids have prominent and sometimes elaborate mouth markings, including patterns of black spots and/or lines on the palate and papillae of different sizes, shapes, and colors at the corners of the mouth (Payne 2005). These markings are important in securing parental care from the foster parents (Payne et al. 2001; Schuetz 2005a, 2005b). Most indigobirds show remarkably precise mimicry of the species-specific mouth patterns of their respective hosts (Figure 1).

Second, adult male indigobirds mimic the songs of their respective hosts (Payne 1973, 1976, 1982). Recent captive studies (Payne et al. 1998, 2000) have demonstrated that male village indigobirds (V. chalybeata) imprint on the songs of their foster parents as juveniles and mimic the songs of their host species as adults. Female indigobirds also imprint on songs of the host species and use these songs to choose both mates and the nests they parasitize.